The present invention relates to heating device, and more particularly relates to a heating device of which an electrically insulating film and protection film for covering a heating member are improved.
Japanese Patent Application Laid-Open 2000-2571 discloses a hot-wire microheater as a heating device having a heating member and an electrically insulating thin film for protecting the heating member. A sectional view of the hot-wire microheater as disclosed in the publication is shown in FIG. 1. Referring to FIG. 1, a hot-wire microheater 101 includes: a substrate 102 made for example of silicon; an electrically insulating film 103 provided on the substrate 102; Si3N4 film 104 provided on the electrically insulating film 103; a heating member 105 provided on the Si3N4 film 104; and a protection film 106 laminated so as to cover the Si3N4 film 104 and heating member 105. Further, a hollow 107 is formed at a portion of the substrate 102 corresponding to the underneath of the heating member 105, so as to achieve a thermal insulation between the heating member 105 and the substrate 102.
The abovementioned publication also discloses a hot-wire microheater of another construction. A sectional view of the hot-wire microheater having such construction is shown in FIG. 2. Referring to FIG. 2, hot-wire microheater 101 includes: a substrate 102; an electrically insulating film 103 provided on a surface of the substrate 102; a heating member 105 made of a resistance member provided on the insulating film 103; a first protection film 108 for covering the heating member 105 and the insulating film 103; a reinforcing section 109 for covering a region of the first protection film 108 corresponding to the heating member 105; a second protection film 110 for covering the reinforcing section 109 and the first protection film 108; and a thermal insulating hollow 107 provided in the substrate 102 corresponding to the underneath of the heating member 105. It is then said that the first protection film 108 and second protection film 110 may be formed of SiO2, Si3N4, alumina (Al2O3), or magnesia (MgO), or a composite of these. Further it is said that the reinforcing section 109 is formed of Si3N4.
A thin-film calorific heater having construction as shown in FIG. 3 is disclosed in Japanese Patent Application Laid-Open Hei-11-31577 as a heating device of another construction having a heating member and an electrically insulating thin film for protecting the heating member. As shown in FIG. 3, thin-film calorific heater 201 includes: a plurality of unit heating member 203 formed as a thin film coating of a certain pattern on a substrate 202; and a protection film 205 formed as applied on an upper surface of the unit heating members 203 and electrodes 204 thereof so as to provide protection therefor. It is said therein that the protection film 205 is formed of one selected from Si3N4, SiO2, or SiC.